I recently tried to install Vista on my computer. For one reason or another, it would not work when I installed it on my C: drive. After an hour or so of playing with it, I was able to install it on my Backup partition (D. Now when it boots up, all my programs do not boot up with it automatically as it would if Windows was installed on my C: drive. Now, I want to delete the version that does not work on my C: Drive, and move the version that does work from my D: partition to my C: Drive. How do I do that?

What else is on this drive?

If nothing worth saving I'd suggest reinstalling a Clean Install and format the drive.

If you want to partition the drive in advance GParted is a good tool for that:

http://gparted.sourceforge.net/livecd.php

Otherwise are you trying to setup a dual boot system? Are you trying to preserve another Operating System? A Clean Install should disregard any previous data on the partition therefore making an old C: moot.

If we are missing your point please post more details as to what you tried and how it went wrong.

The computer boots from the operating system on the D: drive which is pretty small. I want to put this operating system on the C: Drive so it can boot from that drive as my C: drive has all of my important programs and files.

If you are Clean Installing Vista you cannot do this. All programs will have to be reinstalled.

If you are Upgrading from XP to Vista then choose the Vista option of an Upgrade or Repair Install on your XP (or C: drive).